caffeine

noun

caf·​feine ka-ˈfēn 

ˈka-ˌfēn

: a bitter alkaloid C₈H₁₀N₄O₂ found especially in coffee, tea, cacao, and kola nuts and used medicinally as a stimulant and diuretic

Examples of caffeine in a Sentence

Her doctor told her to avoid caffeine.

Recent Examples on the Web

The store’s protein aisle sits alongside a growing lineup of ready-to-drink iced coffees and instant coffee, giving shoppers a way to build a caffeine-and-protein routine for a fraction of what a coffee shop run would cost. — Lauren Jarvis-Gibson july 16, Kansas City Star, 16 July 2026

Stretching a grocery budget without giving up your morning caffeine fix or your protein goals is a challenge, and Dollar Tree has quietly become a destination for shoppers trying to do both. — Lauren Jarvis-Gibson july 16, Miami Herald, 16 July 2026

Because some of my earliest departures happen before my neighborhood coffee shop or even the airport lounge opens, caffeine is a non-negotiable. — Jacqueline Dole, Travel + Leisure, 16 July 2026

Combining caffeine with protein in one drink means alertness and focus from the coffee alongside the nutrients that keep muscles healthy. — Lauren Jarvis-Gibson, Charlotte Observer, 15 July 2026

Word History

Etymology

German Kaffein, from Kaffee coffee, from French café

First Known Use

circa 1823, in the meaning defined above

Phrases Containing caffeine

• caffeine-free

Rhymes for caffeine

• agin
• alkene
• allene
• ameen
• amin
• arene
• athene
• baleen
• beeline
• benzene
• between
• bromine

Kids Definition

caffeine

noun

caf·​feine ka-ˈfēn 

ˈka-ˌfēn

: a bitter stimulating compound found especially in coffee, tea, cacao, and kola nuts

Medical Definition

caffeine

noun

caf·​feine ka-ˈfēn, ˈka-ˌ; ˈkaf-ē-ən 

: a bitter alkaloid C₈H₁₀N₄O₂ found especially in coffee, tea, and kola nuts and used medicinally as a stimulant and diuretic

caffeinic

ka-ˈfē-nik  ˌkaf-ē-ˈin-ik 

adjective